Maximizing completeness in single-crystal high-pressure diffraction experiments: phase transitions in 2°AP

Sufficiently high completeness of diffraction data is necessary to correctly determine the space group, observe solid-state structural transformations or investigate charge density distribution under pressure. Regrettably, experiments performed at high pressure in a diamond anvil cell (DAC) yield inherently incomplete datasets. The present work systematizes the combined influence of radiation wavelength, DAC opening angle and sample orientation in a DAC on the completeness of diffraction data collected in a single-crystal high-pressure (HP) experiment with the help of dedicated software. In particular, the impact of the sample orientation on the achievable data completeness is quantified and proved to be substantial. Graphical guides for estimating the most beneficial sample orientation depending on the sample Laue class and assuming a few commonly used experimental setups are proposed. The usefulness of these guides has been tested in the case of luminescent 1,3-diacetylpyrene, suspected to undergo transitions from the α phase (Pnma) to the γ phase (Pn21 a) and δ phase (P1121/a) under pressure. Effective sample orientation has ensured over 90% coverage even for the monoclinic system and enabled unrestrained structure refinements and access to complete systematic extinction patterns.

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Use of a miniature diamond-anvil cell in a joint X-ray and neutron high-pressure study on copper sulfate pentahydrate

IUCrJ ◽

10.1107/s2052252521010708 ◽

2021 ◽

Vol 9 (1) ◽

Author(s):

Giulia Novelli ◽

Konstantin V. Kamenev ◽

Helen E. Maynard-Casely ◽

Simon Parsons ◽

Garry J. McIntyre

Keyword(s):

High Pressure ◽

Single Crystal ◽

Diffraction Data ◽

Diamond Anvil Cell ◽

Structural Parameters ◽

Structure Refinement ◽

Neutron Data ◽

X Ray ◽

Sulfate Pentahydrate ◽

Diamond Anvil

Single-crystal X-ray and neutron diffraction data are usually collected using separate samples. This is a disadvantage when the sample is studied at high pressure because it is very difficult to achieve exactly the same pressure in two separate experiments, especially if the neutron data are collected using Laue methods where precise absolute values of the unit-cell dimensions cannot be measured to check how close the pressures are. In this study, diffraction data have been collected under the same conditions on the same sample of copper(II) sulfate pentahydrate, using a conventional laboratory diffractometer and source for the X-ray measurements and the Koala single-crystal Laue diffractometer at the ANSTO facility for the neutron measurements. The sample, of dimensions 0.40 × 0.22 × 0.20 mm3 and held at a pressure of 0.71 GPa, was contained in a miniature Merrill–Bassett diamond-anvil cell. The highly penetrating diffracted neutron beams passing through the metal body of the miniature cell as well as through the diamonds yielded data suitable for structure refinement, and compensated for the low completeness of the X-ray measurements, which was only 24% on account of the triclinic symmetry of the sample and the shading of reciprocal space by the cell. The two data-sets were combined in a single `XN' structure refinement in which all atoms, including H atoms, were refined with anisotropic displacement parameters. The precision of the structural parameters was improved by a factor of up to 50% in the XN refinement compared with refinements using the X-ray or neutron data separately.

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Structure solution and refinement from powder or single-crystal diffraction data? Pros and cons: An example of the high-pressure β′-polymorph of glycine

Powder Diffraction ◽

10.1154/1.2999248 ◽

2008 ◽

Vol 23 (4) ◽

pp. 307-316 ◽

Cited By ~ 24

Author(s):

Nickolay A. Tumanov ◽

Elena V. Boldyreva ◽

Hans Ahsbahs

Keyword(s):

High Pressure ◽

Single Crystal ◽

Powder Diffraction ◽

Diffraction Data ◽

Structural Model ◽

Single Crystal Diffraction ◽

X Ray ◽

Pros And Cons ◽

Diamond Anvil ◽

The Difference

The structure of a high-pressure polymorph of glycine (the β′-polymorph formed reversibly at 0.8 GPa from the β-polymorph) was determined from high-resolution X-ray powder diffraction data collected in situ in a diamond anvil cell at nine pressure points up to 2.6 GPa. X-ray powder diffraction study gave a structural model of at least the same quality as that obtained from a single-crystal diffraction experiment. The difference between the powder-diffraction and the single-crystal models is related to the orientation of the NH3-tails and the structure of the hydrogen-bonds network. The phase transition between the β- and β′-polymorphs is reversible and preserves a single crystal intact. No transformations were observed between the β-, α-, and β′-polymorphs on compression and decompression, although the α- and β′-polymorphs belong to the same space group (P21/c). The instability of the β- and γ-forms with pressure can be predicted easily when considering the densities of their structures versus pressure. The direction of the transformation (i.e., which of the high-pressure polymorphs is formed) is determined by structural filiation between the parent and the high-pressure phases because of the kinetic control of the transformations.

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Single Crystal Growth and Physical Properties of Pyroxene CoGeO3

Crystals ◽

10.3390/cryst11040378 ◽

2021 ◽

Vol 11 (4) ◽

pp. 378

Author(s):

Li Zhao ◽

Zhiwei Hu ◽

Hanjie Guo ◽

Christoph Geibel ◽

Hong-Ji Lin ◽

...

Keyword(s):

High Pressure ◽

Magnetic Properties ◽

Magnetic Susceptibility ◽

Crystal Growth ◽

Physical Properties ◽

Single Crystal ◽

Single Crystals ◽

Magnetic Moments ◽

Single Crystal Growth ◽

The Impact

We report on the synthesis and physical properties of cm-sized CoGeO3 single crystals grown in a high pressure mirror furnace at pressures of 80 bar. Direction dependent magnetic susceptibility measurements on our single crystals reveal highly anisotropic magnetic properties that we attribute to the impact of strong single ion anisotropy appearing in this system with TN∼33.5 K. Furthermore, we observe effective magnetic moments that are exceeding the spin only values of the Co ions, which reveals the presence of sizable orbital moments in CoGeO3.

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Comparison between beryllium and diamond-backing plates in diamond-anvil cells: Application to single-crystal x-ray diffraction high-pressure data

Review of Scientific Instruments ◽

10.1063/1.3590776 ◽

2011 ◽

Vol 82 (5) ◽

pp. 055111 ◽

Cited By ~ 7

Author(s):

Benedetta Periotto ◽

Fabrizio Nestola ◽

Tonci Balic-Zunic ◽

Ross J. Angel ◽

Ronald Miletich ◽

...

Keyword(s):

High Pressure ◽

Single Crystal ◽

Pressure Data ◽

X Ray Diffraction ◽

Diamond Anvil Cells ◽

X Ray ◽

Diamond Anvil

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Microporous crystal structure of labuntsovite-Fe and high-pressure behavior up to 23 GPa

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s205252061700498x ◽

2018 ◽

Vol 74 (1) ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Sergey M. Aksenov ◽

Elena A. Bykova ◽

Ramiza K. Rastsvetaeva ◽

Nikita V. Chukanov ◽

Irina P. Makarova ◽

...

Keyword(s):

Crystal Structure ◽

High Pressure ◽

Single Crystal ◽

Cross Section ◽

Structure Refinement ◽

Alkaline Complex ◽

X Ray ◽

Cell Parameters ◽

Diamond Anvil ◽

The Stability

Labuntsovite-Fe, an Fe-dominant member of the labuntsovite subgroup, was first discovered in the Khibiny alkaline massif on Mt Kukisvumchorr [Khomyakov et al. (2001). Zap. Vseross. Mineral. Oba, 130, 36–45]. However, no data are published about the crystal structure of this mineral. Labuntsovite-Fe from a peralkaline pegmatite located on Mt Nyorkpakhk, in the Khibiny alkaline complex, Kola Peninsula, Russia, has been investigated by means of electron microprobe analyses, single-crystal X-ray structure refinement, and IR and Raman spectroscopies. Monoclinic unit-cell parameters of labuntsovite-Fe are: a = 14.2584 (4), b = 13.7541 (6), c = 7.7770 (2) Å, β = 116.893 (3)°; V = 1360.22 (9) Å3; space group C2/m. The structure was refined to final R 1 = 0.0467, wR 2 = 0.0715 for 3202 reflections [I > 3σ(I)]. The refined crystal chemical formula is (Z = 2): Na2K2Ba0.7[(Fe0.5Ti0.1Mg0.05)(H2O)1.3]{[Ti2(Ti1.9Nb0.1)(O,OH)4][Si4O12]2}·4H2O. The high-pressure in situ single-crystal X-ray diffraction study of the labuntsovite-Fe has been carried out in a diamond anvil cell. The labuntsovite-type structure is stable up to 23 GPa and phase transitions are not observed. Calculations using the BM3 equation of state resulted in the bulk modulus K = 72 (2) GPa, K′0 = 3.7 (2) and V 0 = 1363 (2) Å3. Compressing of the heteropolyhedral zeolite-like framework leads to the deformation of main structural units. Octahedral rods show the gradual increase of distortion and the wave-like character of rods becomes more distinct. Rod deformations result in the distortion of the silicon–oxygen ring which is not equal in different directions. Structural channels are characterized by a different ellipticity–pressure relationship: the cross-section of the largest channel I and channel II demonstrates the stability of the geometrical characteristics which practically do not depend on pressure: ∊channel I ≃ 0.85 (4) (cross-section is rather regular) and ∊channel II ≃ 0.52 (2) within the whole pressure range. However, channel III is characterized by the increasing of ellipticity with pressure (∊ = 0.40 → 0.10).

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Indexing of multi-particle diffraction data in a high-pressure single-crystal diffraction experiment

Journal of Applied Crystallography ◽

10.1107/s0021889812051886 ◽

2013 ◽

Vol 46 (2) ◽

pp. 387-390 ◽

Cited By ~ 3

Author(s):

Hui Li ◽

Xiaodong Li ◽

Meng He ◽

Yanchun Li ◽

Jing Liu ◽

...

Keyword(s):

Genetic Algorithm ◽

High Pressure ◽

Single Crystal ◽

Single Crystals ◽

Diffraction Data ◽

Reciprocal Lattice ◽

Powder Pattern ◽

Diffraction Experiment ◽

Crystal Data ◽

Single Crystal Diffraction

High-pressure single-crystal diffraction experiments often suffer from the crushing of single crystals due to the application of high pressure. Consequently, only diffraction data resulting from several particles in random orientations is available, which cannot be routinely indexed by commonly used methods designed for single-crystal data. A protocol is proposed to index such diffraction data. The techniques of powder pattern indexing are first used to propose the possible lattice parameters, and then a genetic algorithm is applied to determine the orientation of the reciprocal lattice for each of the particles. This protocol has been verified experimentally.

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